Re: [Xen-devel] [PATCH 2/2] xen: make opt_xen_console true before console initialisation

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Sep 28, 2018 at 04:23:24PM +0100, Wei Liu wrote:
> On Fri, Sep 28, 2018 at 09:19:56AM -0600, Jan Beulich wrote:
> > >>> On 28.09.18 at 17:12, <wei.liu2@xxxxxxxxxx> wrote:
> > > On Fri, Sep 28, 2018 at 09:08:34AM -0600, Jan Beulich wrote:
> > >> >>> On 28.09.18 at 10:24, <wei.liu2@xxxxxxxxxx> wrote:
> > >> > --- a/xen/drivers/char/console.c
> > >> > +++ b/xen/drivers/char/console.c
> > >> > @@ -91,7 +91,8 @@ static uint32_t conringc, conringp;
> > >> >  static int __read_mostly sercon_handle = -1;
> > >> >  
> > >> >  #ifdef CONFIG_X86
> > >> > -static bool __read_mostly opt_console_xen; /* console=xen */
> > >> > +/* Set to true at start of day to catch early boot issues */
> > >> > +static bool __read_mostly opt_console_xen = true; /* console=xen */
> > >> 
> > >> When Andrew suggested this, iirc he said to make the variable
> > >> tristate. Otherwise ...
> > > 
> > > I figure it doesn't need to be tristate.
> > > 
> > >> 
> > >> > @@ -821,6 +822,10 @@ void __init console_init_preirq(void)
> > >> >  
> > >> >      serial_init_preirq();
> > >> >  
> > >> > +#ifdef CONFIG_X86
> > >> > +    opt_console_xen = false;
> > >> > +#endif
> > >> 
> > >> ... you possibly override a user specified "true" here.
> > > 
> > > Do I? This is right before option parsing, during which opt_console_xen
> > > is set.
> > 
> > Hmm, I see - I didn't recall we still have this ad hoc parsing in
> > place, instead of using custom_param(). But isn't this too early then,
> > as messages issued from the parsing code then would not be visible?
> 
> To me it doesn't make anything worse than before. But I see your point.
> I will see if there is an easy way to fix this.

At the moment the ordering of the options matter, which means if "xen"
is not the first option we can lose output.

I think one easy way of improving is to parse opt_console twice. The
first time solely looks for "xen" and the second time parses the rest
options.


Wei.

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